A mainland woman might be planning to board a flight from the mainland to Hong Kong with a bomb, Taiwanese authorities have warned.
Taiwan's airport police are on alert after receiving the intelligence from the island's National Security Bureau.
A source in Taiwan's airport police said the intelligence described the woman as being long-haired and that she might board a Dragonair or Cathay Pacific flight to Hong Kong today or tomorrow. The intelligence gave no further details.
Jeff Sun Jianfeng, vice-president of Hong Kong Airlines, confirmed that the airline had responded to the threat by sending an alert to all ground staff, cabin crew and pilots.
The document reads: "Information received that a Security THREAT might occur on flights to/from China and Hong Kong on the coming 2 days.
"[All] flights to/from China and Hong Kong on 06-07Jun2014 are required to apply for Enhanced Flight Deck Entry/Exit Procedure and crews are required to raise their awareness of in-flight security."
But Sun said it was only a "low-level" alert.
Repeated calls last night to the Ministry of Public Security and the Civil Aviation Administration in Beijing were unsuccessful. The Civil Aviation Department in Hong Kong said it had no comment to make.
Cathay and Dragonair said they had been informed of the threat and that their front-line teams had been reminded to remain vigilant as usual. They would also work closely with the relevant authorities.
A commercial pilot said airlines occasionally received such alerts, such as four years ago when the World Cup was held in South Africa. But this was "very rare" as the alert was so specific about the days.
An officer at Taiwan's Aviation Police Bureau said: "We have been asked by relevant authorities to exercise extra scrutiny in our inspection of all inbound and outbound passengers' belongings, including hand-carry ones, though the intelligence about the possible security check is not related to Taiwan."
A Hong Kong police source said they were also aware of the report and that officers had been "monitoring closely" terrorist- related activities on the mainland and worldwide. They had been exchanging terrorist-related intelligence with other law enforcement authorities on a daily basis.
A police spokesman said they had no solid intelligence to show the city was a target of terrorism and the "moderate" alert level would remain.
So far, Taiwan police had not found anything suspicious, the airport police officer said.
Additional reporting by Adrian Wan and Li Jing